Mike Wierzbicki
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 Feb19 comment How to get from $a\sqrt{1 + \frac{b^2}{a^2}}$ to $\sqrt{a^2 + b^2}$ Hint: for positive $a$, $a = \sqrt{a^2}$. Feb6 comment Time Series and statistics @Probabilityman Oops, sorry about that. Feb6 revised Time Series and statistics fixed my mistake Feb6 suggested approved edit on Time Series and statistics Feb6 comment Time Series and statistics @DilipSarwate Ah sorry, yes I think you're correct. It was previously written as (Xt - j) and I didn't even think about whether it should be X(t)-j or X(t-j). The latter makes much more sense. Feb6 revised Time Series and statistics fixed typos and added latex Feb6 suggested approved edit on Time Series and statistics Jan18 answered Mathematical toys? Jan18 comment Mathematical toys? Define "serious." Jan18 awarded Fanatic Jan16 comment Generalization of variance to random vectors Note: the covariance matrix contains covariances, not correlations (i.e. the elements are not constrained to $[-1,1]$). Further note: the diagonals of the covariance matrix are variances. Nov30 revised finding interval where inequality holds fixed up the TeX Nov30 suggested approved edit on finding interval where inequality holds Nov24 answered Puzzle: numerical pattern recognition Nov23 answered Ways to teach fractions Nov9 awarded Enthusiast Nov4 comment Finding a formula to sum natural numbers up to $n$ I love this trick -- usually blows the mind of at least one student when shown to them. Can you do something similar for the sum of squares, cubes, etc? Nov4 comment Working out the variance of the Poisson distribution Take a look at factorial moments and factorial moment generating functions (That's what he's using). Nov2 revised Confused about modular notations added latex and relevant tags Nov2 suggested approved edit on Confused about modular notations